In recent years, manual cardiopulmonary resuscitation (CPR) techniques for reproducing the cardiac and pulmonary functions of a patient have been taught to and used by paramedics, emergency medical technicians, and the general public. Although manual CPR techniques differ somewhat, a typical technique that is designed for use by a single person comprises the following steps. The person first clears the patient's airway (e.g., the mouth, larynx, and the trachea), by removing any obstructions therein, and by tilting the patient's head back and by elevating the patient's chin. After the airway has been cleared, the person reproduces the pulmonary function by breathing into the patient's mouth to inflate the patient's lungs through the airway. The person then reproduces the cardiac function by compressing the patient's chest immediately above the sternum at a predetermined rate, e.g., 80 compressions per minute, in order to compress the patient's heart so as to force blood through the patient's circulatory system. Since a single person cannot both compress the patient's chest and breathe into the patient's mouth at the same time, the technique involves repetitive cycles of a predetermined number of chest compressions, e.g., fifteen, followed by a predetermined number of breaths into the mouth, e.g., two.
Although manual CPR techniques have saved countless lives, they are subject to the disadvantage that they must be used by a person who has been trained in these techniques. In order to have any chance of restoring the patient to normal health, CPR must be started within a certain period of time after the paitent has been stricken. Accordingly, if a trained person is not readily available, the patient will most likely die. Another disadvantage of manual CPR techniques is that they are relatively inefficient in reproducing the cardiac and pulmonary functions. For example, manual CPR techniques can at best result in only a small percentage of the normal blood flow to the patient's brain and only a small percentage of the normal oxygenation of the patient's blood through lung inflation.
The efficiency of CPR may be increased by the used of automated CPR apparatus, sometimes referred to as resuscitators. Although the structure and operation of resuscitators differ, they typically include a reciprocable chest plunger that is positioned by an appropriate mounting frame above the patient's chest or that is secured to the patient's chest by a plurality of straps, and an airway apparatus including a mouth piece which is inserted into the patient's mouth. An appropriate driving means causes the reciprocable chest plunger to be extended to and from the patient's chest so as to compress the heart, and a pressurized air or oxygen source is coupled to the airway apparatus so as to inflate the patient's lungs. Typically, the apparatus is operated in a cyclical mode, each cycle including a plurality of successive chest compressions (e.g., five) followed by a single airway pressurization.
Such automated CPR apparatus are bulky and heavy, and therefore not easily transportable. They also require an external source of power (such as a source of compressed oxygen), and are difficult to use by all but highly-trained paramedics and emergency medical technicians. Therefore, despite their increased efficiency, such automated CPR apparatus generally are not available for use, or are used, by the general public.
Recently, it has been discovered that the mechanism for causing blood to flow through the circulatory system during CPR may not be the force that is transmitted to the heart through the chest during each chest compression, as previously thought, but rather the amount of intrathoracic pressure that is generated in that portion of the thorax in which the heart and lungs are located. It therefore has been postulated that an increase in intrathoracic pressure during CPR should increase the efficiency of CPR. Reference, for example, Rudikoff et al., Mechanisms Of Blood Flow During Cardiopulmonary Resuscitation, CIRCULATION, v. 61, No. 2, pp. 345-352 (1980). However, no practical manual CPR apparatus has yet been devised which utilizes this discovery to accordingly increase the intrathoracic pressure of the patient during CPR.
It is therefore an object of this invention to provide a manually-actuable CPR apparatus.
It is another object of this invention to provide such an apparatus which operates by increasing the intrathoracic pressure of the patient.
It is yet another object of this invention to provide such an apparatus which provides more efficient CPR than currently-used manual CPR techniques.
It is a further object of this invention to provide such an apparatus which is small in size and light in weight, and therefore easily transportable, which requires no external source of power other than that provided by the user, which is constructed from ready-available components, and which is easy to use by relatively unskilled persons.